Driving mechanism



y 1965 s. A. YOUNG v 3,182,518

DRIVING MECHANISM Filed Jan. 2, 1963 3 Sheets-Sheet l May 11, 1965 s, A, YOUNG 3,182,518

DRIVING MECHANISM Filed Jan. 2, 1963 I5 Sheets-Sheet 2 Tlilll Illllll 1 "28 *2 LJF M i1.

y 1, 1965 Q s. A. YOUNG 3,182,518

DRIVING MECHANISM Filed Jan. 2, 1963 3 Sheets-Sheet 3 United States Patent 3,182,518 DRIVING MECHANISM Sidney A. Young, East Kilhride, Scotland, assignor to The Hoover Company, North Canton, Ohio, a corporation of Ohio Filed Jan. 2, 1963, Ser. No. 248,940 12 Claims. (Cl. 74-425) This invention relates to cam mechanism for imparting movement to a cam follower, and is concerned with arrangements embodying a reversible driving means for driving the cam. Particularly the cam mechanism is applicable to timing devices wherein a unidirectional stepby-step movement is required irrespective of the direction of rotation of the driving means. In such timing devices it is generally desirable that the step movement should be a quick one in order to make or break electrical contacts in the device quickly.

It is therefore a primary object of the present invention to provide a cam mechanism including a cam follower which is caused to make a step movement of short duration.

To that end the invention provides an arrangement comprising first and second members the first comprising a cam driven by a reversible shaft, and the second member a cam follower to engage the cam, one of the members having pivotally mounted on it a dog which is rockable by its engagement with the other member between two positions, the said engagement causing it to rock to one position in one direction of rotation of the cam and to rock to the other position in the opposite direction of rotation of the cam, the dog presenting to the other member when in each position, a gradually rising face of engagement and a steeply falling opposite face.

This invention may be carried into practice in a number of ways but one specific embodiment will now be described by way of example with reference to the accompanying drawings in which:

FIGURE 1 is a diagrammatic sectional side elevation of a dish washer incorporating mechanism according to the present invention;

FIGURE 2 is an end elevation of the reversible electric motor and showing certain parts of a driving mechanism for the programme cam of the dish washer;

FIGURE 3 is a partial section side elevation on a line II-II of FIGURE 2.;

FIGURE 4 is a partial section perspective view showing the drive mechanism between the motor and the programme cam;

FIGURE 5 is an enlarged partial section view of part of the drive mechanism generally on the line 1VIV of FIGURE 3 with the motor running in one direction;

FIGURE 6 is a view similar to FIGURE 5 but showing the operation with the motor running in the opposite direction, and;

FIGURE 7 is a diagrammatic detail of the pawl and its stop.

As shown in FIGURE 1 of the drawings a dish washer, generally indicated at 100, includes an outer shell 10=1 surrounding an inner cabinet 102 which receives dishes etc., in the usual way on racks 103. Extending from front to back across the bottom of the cabinet 102 is a rotary impeller 105 which serves to spray washing liquid upwards amongst the dishes or other articles supported on the racks 103. The impeller 105 is driven about a horizontal axis by means of a chain and sprocket drive 106 from one end of the shaft 115 of a motor 107. As shown in FIGURE 1 the motor 107 is mounted beneath the inner cabinet 102 and in addition drives an emptying pump 108. The pump is of positive type and permanently connected to be driven by the shaft of the motor by ice means of a drive mechanism 109. The motor 107 is reversible so that the pump 108 removes liquid from the cabinet when the motor is running in one direction but not in the other.

The other end of the motor shaft 115 is connected to a timing mechanism 110 through a driving mechanism which is illustrated in detail in FIGURES 2-7.

FIGURES 2 and 3 show parts of the driving and timing mechanism including a timing cam 11 by which a number of pairs of contacts (not shown) are operated at certain times in order to carry out the correct sequence of operations of the dish washer. The cam 11 is of disc form and is provided on one face with a number of circular grooves (not shown) and which have suitable steps to co-operate with cam followers which operate the contacts. The manner in which these contacts are operated is conventional and forms no part of the present invention. Accordingly these parts have been omitted for the sake of simplicity and clarity. The whole of the periphery of the cam disc 11 is formed with a series of teeth 12 by which the cam may be indexed round in a manner to be described.

Extending outwards from the end frame of the motor 107 are four pillars 13 upon which is mounted a supporting plate 14 in which the cam disc 11 is journalled, as shown in FIGURE 3. The end of the motor shaft carries a short worm 16 which meshes with a worm wheel 18, which is more clearly seen in FIGURE 4. The worm wheel 18 is formed integrally with a stub shaft 19 at the end of which is a second worm 20. The stub shaft 19 rotates in a bore 21 in a boss 22 secured to, or forming part of, the end frame of the motor. As shown in FIGURE 4 the axis of the first worm wheel 18 and the second worm 29 is set at slightly more than a right angle to the axis of the motor shaft 115, i.e. 90 plus the lead angle of the first worm 16. The teeth of the first worm wheel however, extend parallel to its axis, as shown in FIGURE 4, so that its teeth correctly engage the teeth of the worm 16, but the drive is transmitted through greater than a right angle.

The second worm 20 drives a second wormwheel 25, most clearly seen in FIGURE 3. This worm wheel rotates on a fixed shaft 26 (FIGURE 4) extending parallel to, .but offset from, the shaft 115 of the motor. Here again the second worm wheel 25 has teeth extending parallel to the axis of the shaft 26. Further, the axis of the second worm wheel 25 similarly lies with respect to the axis of the worm 20, at 90 plus the lead angle of the second worm 20. Hence the teeth of the second worm and worm wheel correctly engage despite the fact that the worm wheel has straight teet f This arrangement therefore imparts a double reduction in speed between the motor shaft 115 and the second worm wheel 25. The fact that the teeth of the two worm wheels are straight enables these to be produced of a plastic material, for example, nylon, by simple moulding processes which do not require complicated dies. In contrast, moulded worm wheels with the usual helical teeth require a complicated and expensive moulding process, in some instances the die requiring six parts.

Reference will now be made to the arrangement by which the second worm wheel 25 imparts a step by step movement to the programme cam 11 in one direction irrespective of the direction of rotation of the electric motor 107. To this end the second worm wheel 25 has secured to one end face a metal disc 28, the surface of the end face of the worm wheel directly beneath this disc being cut out to the somewhat keyhole shape indicated at 20 in FIGURES 4-6. A short pivot pin 30 extends across this cut out region and pivoted to this pin is a driving dog 33 which, as shown in FIGURES 4-6, projects from the periphery of the worm wheel 25. As shown in FIGURE 3 the dog comprises a small flat member and as shown in FIGURES 5 and 6 the projecting part of the dog affords a pair of symmetrical cam surfaces 34, merging together by means of a smoothly rounded point 35. The dog can tilt to either side of a mean position in which the two cam surfaces 34 lie symmetrically disposed in relation to a radius extending through the centre of the second worm wheel and the pivot pin 30.

The tilting movement on either side of this mean position is limited by engagement of the other end of the dog with one of two abutment surfaces 37 forming part of the boundery of the cut-out 29. These two positions are shown respectively in FIGURES 5 and 6. In each position it will be seen that one of the cam surfaces 34 affords a gradually rising surface extending from the periphery of the worm wheel 25 whilst the other forms a steeply falling surface with respect to this periphery.

Arranged to co-operate with the dog is an idler roller 40 which is carried, as shown in FIGURES 3 and 5 between the arms of a U shaped support 41, the lower ends of the arms of which are pivoted by means of a pin 42 to the supporting plate 14. As shown in FIGURE 2 the U-shaped support 41 is spring biased by means of a tension spring 43 so that the roller 40 is biased towards the periphery of the metal disc 28.

The U-shaped support 41 has a transverse pin 44 extending across it to support the roller 40 and, on the side remote from the worm wheel 25, this transverse pin carries a small pawl 46 provided with a small torsion spring 47 which biasses it into engagement with the teeth 12 around the periphery of the programme cam 11. A spring stop 49 is provided to prevent anti-clockwise movement of the cam 11 from the position shown in FIGURE 2.

Referring to FIGURE 2 and in detail to to FIGURE 7 it will be seen that a further stop is provided which has an angled face to engage the pawl and arrest its forward movement. This ensures that any tendency for the cam disc 11 to overun is limited or prevented.

Operation of this device is as follows:

Assuming firstly that the motor 107 is rotating in a clockwise direction as viewed in FIGURE 2, then the second worm wheel 25 will also be rotated in a clockwise direction as shown in FIGURE 6. Therefore, after a predetermined period of time the dog 33 will engage the roller 40 and be tilted to the position shown in FIGURE 6. Thereafter further rotation of the worm wheel 25 will cause the roller 40 to ride up the leading cam surface 34, in this case the lower surface, and so pivot the U-shaped support 41 away from the worm wheel 25. Referring to FIGURE 2, this movement is seen to carry the pawl 46 back over one tooth of the programme cam 11. As soon as the roller 40 reaches the smoothly rounded point 35 of the dog 33 it will quickly drop down the other side of the dog since the trailing surfaces 34 then lies at quite a steep angle (almost radial) with respect to the periphery of the worm wheel 25. This return movement of the roller is caused by the action of the tension spring 43 which at the same time causes the pawl 46 to index the timing cam forward one step. The fact that this movement is a quick one is of considerable importance since the contacts operated by the timing cam are quickly opened or closed.

If the motor 107 is rotating in the opposite direction a precisely similar operation occurs as shown in FIGURE 5. In this case the pawl 33 is tilted as soon as it engages the roller 40 on its underside and likewise the roller rides up the then upper leading surface 34 and drops quickly down the lower trailing surface.

In the particular embodiment described the double reduction obtained by the two worm and worm wheel trains gives the second worm wheel 25 a speed of rotation of approximately one revolution every 17 seconds. Hence if the motor continues to rotate in a given direction, the programme cam will be indexed forward one step every 17 seconds. If, however the motor 10 is reversed by the closing or opening of some contacts of the programme cam 11 at any position, the second worm wheel 25 will reverse its direction of rotation immediately, the roller dropping down a trailing surface of the dog 33. Accordingly the dog will again engage the roller 40 and move it up the same (but now leading) surface of the dog, this taking approximately 2 seconds. The roller then drops down and the now trailing surface so that the pawl 46 again indexes the programme cam forward one step. --1ence on this occasion the programme will be indexed forward after 2 seconds instead of the usual 17 seconds.

In other words, every time the direction of rotation of the motor is reversed only a two second period will elapse before the cam is again indexed. If desired, this two second period can be employed for the whole of a particular operation. For example, as shown in FIGURE 1, the dish washer has a pair of reservoirs 112 and 113 respectively containing liquid detergent and wetting agent which can be injected into the cabinet 102 by means of valves 114 and 115 respectively. These valves are arranged to receive, through cables 116 and 117 respectively only a two second impulse during one of the two second timing periods referred to above, and the valve settings are such that during the two second periods the required quantity of either detergent or wetting agent is admitted.

Various modifications may be possible. In particular it will be appreciated that the use of a pivoted dog could be made where this acts as a cam follower to be engaged by an eccentric cam.

What I claim as my invention and desire to secure by Letters Patent is:

1. In a driving mechanism, a first member defining driving means rotatably mounted on a support for selective clockwise or counterclockwise rotation, a second member defining driven means mounted for reciprocatory movement adjacent said first member, means biasing said second member to a static position against a stop, contact means on one of said members, a pair of oppositely facing cam surfaces on the other of said members, the slope of said cam surfaces being substantially equal, one of said pair of cam surfaces being engageable with said contact means upon clockwise rotation of said first member and the other of said pair of cam surfaces being engageable with said contact means upon counterclockwise rotation of said first member, rotation of said first member in either direction causing one or the other of said cam surfaces to engage said contact means and cam said second member away from said stop against the force of said biasing means, said second member being free to quickly snap back to said static position immediately after said contact means reaches the terminus of the cam surface against which it is engaged regardless of the direction of rotation of said first member.

2. The driving mechanism of claim 1 wherein said pair of oppositely facing cam surfaces are on a dog which is pivotally secured to said other member for pivotal movement between two positions and said second member reciprocates toward and away from said first member whereby when said dog is in one of said two positions and said contact means moves off of the terminus of the cam surface against which it is engaged said second member moves toward said first member under influence of said biasing means thereby causing said contact means to strike the opposite cam surface and pivot said dog toward the other of said two positions so that said second member is free to quickly snap back against said stop immediately after said contact means moves off of the terminus of the cam surface against which it is engaged.

3. The driving mechanism of claim 1 wherein said second member has a pawl thereon and further including a ratchet wheel rotatably mounted adjacent said pawl, said pawl being engageable with said ratchet wheel upon reciprocatory motion of said second member to rotate said ratchet wheel in a step-by-step fashion, said pawl moving said ratchet wheel one increment in each complete revolution of said first member and means for reversing the direction of rotation of said first member immediately after said pawl moves said ratchet wheel one increment whereby said second member will be reciprocated and cause said pawl to move said ratchet wheel another increment in a small fraction of the time it would take if said first member were left to rotate in a constant direction.

4. A driving mechanism for converting rotary motion to reciprocatory motion comprising, a first member defining driving means rotatably mounted on a support for selective clockwise or counterclockwise rotation, a second member defining driven means mounted for reciprocatory movement adjacent said first member, resilient means biasing said second member to a static position, contact means on one of said members, a dog pivotally mounted on the other of said members, said dog being engageable with said contact means and being pivotable between first and second positions, said dog being pivoted to a first of said positions by engagement with said contact means upon clockwise rotation of said first member, said dog being pivoted to the second of said positions by engagement with said contact means upon counterclockwise rotation of said first member, said dog presenting to said contact means a gently sloping engagement surface and a steeply sloping opposite surface in each of said positions.

5. The driving mechanism of claim 4 wherein said second member is elongated and is pivoted at one end and free at its other end, the free end of said second member reciprocating back and forth with an oscillatory motion upon rotation of said first member, a pawl on the free end of said second member, and a toothed ratchet wheel rotatably mounted adjacent said pawl, the teeth on said ratchet wheel being engageable with said pawl upon reciprocatory movement of said second member whereby said pawl drives said ratchet wheel in one direction regardless of the rotary direction of said first member.

6. A driving mechanism for converting rotary motion to reciprocatory motion comprising, a first member defining driving means rotatably mounted on a support for selective clockwise or counterclockwise rotation, a second member defining driven means mounted for reciprocatory movement adjacent said first member, resilient means biasing said second member to a static position, cooperative engagement means on each of said first and second members for biasing said second member out of said static position when said first member is rotated, said engagement means on one of said first and second members comprising a pivoted dog having a pair of oppositely facing sloping contact surfaces, said dog being pivotable to first and second positions upon selective clockwise or counterclockwise rotation of said first member wherein one or the other of said pair of contact surfaces contacts the engagement means on the other of said members at a gently sloping cam angle and the oppositely facing contact surface falls away sharply regardless of the direction of rotation of said first member.

7. The driving mechanism of claim 6, where when said dog is in one of said two positions and when said engagement means on said other member moves off of the terminus of the contact surface against which it is engaged said second member moves toward said static position under influence of said biasing means thereby causing said engagement means on said other member to strike the opposite contact surface and pivot said dog toward the other of said two positions so that said second member is free to quickly snap back to said static position immediately after said engagement means moves off of the terminus of the contact surface against which it is engaged.

8. A driving mechanism for converting substantially constant rotary motion to step-by-step rotary motion comprising, a first member defining driving means rotatably mounted on a support for selective clockwise or counterclockwise rotation, a second member movably mounted adjacent said first member for movement toward and away from said first member, said second member having a free end, a pawl, on said free end, resilient means biasing said second member toward said first member, a ratchet wheel rotatably mounted on a support adjacent said pawl, cooperative engagement means on each of said first and second members for biasing said second member away from said first member when said first member is rotated, continuous rotation of said first member causing said second member and said pawl to move back and forth under influence of said resilient means and said engagement means, the engagement means on one of said first and second members comprising movable contact means having a pair of contact surfaces, one of said contact surfaces being engageable with the engagement means on the other of said first and second members at a gently sloping biasing cam angle which is substantially the same regardless of the direction of rotation of said first member, said movable contact means presenting a steeply falling opposite surface to the engagement means on the other of said members whereby said second member rapidly snaps back toward said first member under influence of said resilient means after being biased away from said first member by said cooperative engagement means, said pawl being engageable with said ratchet wheel to move said ratchet wheel in a stepby-step rotary motion which is in the same direction regardless of the direction of rotation of said first memher.

9. A driving mechanism for converting selective bidirectional rotary motion of a driving member into oscillating motion of a driven member comprising, a first member defining driving means rotatably mounted on a support for selective clockwise or counterclockwise rotation, a second member mounted for oscillatory movement adjacent said first member, means releasably biasing said second member to a static position, a dog pivotally mounted on one of said first and second members, said dog having a forward contact portion, said forward portion having a pair of sloping surfaces on opposite sides of a plane passing through the longitudinal axis of said dog and the axis about which it is pivoted, said surfaces sloping toward the longitudinal aXis of said dog in a direction from the pivotal aXis of said dog to the tip of said forward portion, said dog being pivotable between a first position in which one of said pair of sloping surfaces defines a first contact cam surface and a second position in which the other of said pair of sloping surfaces defines a second contact cam surface, contact means on the other of said first and second members for engagement with said pair of sloping surfaces whereby when said first member is rotated in a clockwise direction said contact means engages said first contact cam surface to move said dog to said first position and said contact means rides along said first contact cam surface to bias said second member out of said static position, and when said first member is rotated in a counterclockwise direction said contact means engages said second contact cam surface to move said dog to said second position and said contact means rides along said second contact cam surface to bias said second member out of said static position, in each direction of rotation of said first member the contact cam surface which is oppositely facing the contact cam surface being engaged by said contact means presenting a steeply falling surface to said contact means so that said second member rapidly snaps back to said static position after being biased out of said static position by one of said contact cam surfaces, whereby the frequency of the movement of said second member in and out of said static position is substantially the same regardless of the direciton of rotation of said first member.

10. A driving member for a drive mechanism comprising, a wheel having a pair of substantially fiat, spaced apart, oppositely facing side surfaces, a rabbet formed in one of said surfaces and extending from the periphery of said wheel toward the axis thereof, a flat elongated dog member pivotally mounted to said wheel in said rabbet, said dog member having a forward portion projecting beyond the periphery of said wheel, said forward portion having a pair of oppositely facing cam surfaces, said dog member being pivotable between two positions in which its longitudinal axis is on opposite sides of the axis of said wheel and equidistant therefrom in each of said positions, and means on said wheel for limiting pivotal movement of said dog between said two positions.

11. A drive mechanism including first and second members, said first member comprising a rotatably mounted member which is selectively driven in a clockwise or counterclockwise direction by a reversible shaft, the second of said members comprising a follower engageable with said first member, means biasing said follower to a static position, one of said first and second members having a dog pivotally mounted thereon, said dog having a pair of oppositely facing cam surfaces and being rockable between two positions by engagement with the other of said first and second members, in each of said two positions said dog presenting to the other of said first and second members a gradually rising cam surface of engagement and a steeply falling opposite face, whereby the motion imparted to said follower is the same regardless of the direction of rotation of said first member.

12. A drive mechanism as in claim 11 wherein said first member comprises a wheel and said dog is mounted on said wheel.

References Cited by the Examiner UNITED STATES PATENTS 1,627,989 5/27 Nilson 7489 XR 2,866,109 12/58 Wasson 7489 XR 2,964,933 12/60 Fritz 6812 2,997,554 8/61 Cobb et a1. 20038 3,063,299 11/62 Kosbab 74125 FOREIGN PATENTS 558,829 6/58 Canada.

BROUGHTON G. DURHAM, Primary Examiner. 

1. IN A DRIVING MECHANISM, A FIRST MEMBER DEFINING DRIVING MEANS ROTATABLY MOUNTED ON A SUPPORT FOR SELECTIVE CLOCKWISE OR COUNTERCLOCKWISE ROTATION, A SECOND MEMBER DEFINING DRIVEN MEANS MOUNTED FOR RECIPROCATOR MOVEMENT ADJACENT SAID FIRST MEMBER, MEANS BIASING SAID SECOND MEMBER TO A STATIC POSITION AGAINST A STOP, CONTACT MEANS ON ONE OF SAID MEMBERS, A PAIR OF OPPOSITELY FACING CAM SURFACES ON THE OTHER OF SAID MEMBERS, THE SLOPE OF SAID CAM SURFACES BEING SUBSTANTIALLY EQUAL, ONE OF SAID PAIR OF CAM SURFACES BEING ENGAGEABLE WITH SAID CONTACT MEANS UPON CLOCKWISE ROTATION OF SAID FIRST MEMBER AND THE OTHER OF SAID PAIR OF CAM SURFACES BEING ENGAGEABLE WITH SAID CONTACT MEANS UPON COUNTERCLOCKWISE ROTATION OF SAID FIRST MEMBER, ROTATION OF SAID FIRST MEMBER IN EITHER DIRECTION CAUSING ONE OR THE OTHER OF SAID CAM SURFACES TO ENGAGE SAID CONTACT MEANS AND CAM SAID SECOND MEMBER AWAY FROM SAID STOP AGAINST THE FORCE OF SAID BIASING MEANS, SAID SECOND MEMBER BEING FREE TO QUICKLY SNAP BACK TO SAID STATIC POSITION IMMEDIATELY AFTER SAID CONTACT MEANS REACHES THE TERMINUS OF THE CAM SURFACE AGAINST WHICH IT IS ENGAGED REGARDLESS OF THE DIRECTION OF ROTATION OF SAID FIRST MEMBER. 